11'3 Perimeters and Areas of Similar Figures

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11.3 Perimeters and Areas of Similar Figures

• 4.0 Students prove basic theorems involving
  congruence and similarity.
• 8.0 Students know, derive, and solve problems
  involving perimeter, area

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Definitions

• Perimeter of a polygon is the Sum of the lengths
  of the sides of a polygon.
• Area of a polygon- the number of square units
  contained in the interior of a polygon.
• Similar polygons Polygons whose corresponding
  angles are congruent and corresponding sides are
  proportional.

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Example

• Consider similar polygons ABCDEFGH.
• Scale factor Ratio of corresponding sides
• Scale factor______
• Ratio of Perimeters_______
• Ratio of Areas_____

F
E
B
A
2
7
C
B
H
G
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Theorem 11.5 Similar Polygon Thm

• If 2 polygons are similar with scale factor a/b,
  then the ratio of their perimeters is a/b, and
  the ratio of their areas is a2/b2

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Example 2
G

• Scale factor_________
• Ratio of P___________
• Ratio of Areas________

F
H
B
A
C
E
D
I
J
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Example 3

• A regular hexagon has an area of 54 cm square.
  Find the scale factor of this hexagon to a
  similar hexagon that has an area of 150cm square.
  
• A54 A150
• Scale factor___________

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Example 4

• A rectangluar tablecloth is 60 in. by 120 in. A
  similar rectangle placemat made from the same
  cloth is 12 by 24 in and costs 5. Find the cost
  of the tablecloth.
• Hint Give me a statement of proportionality.

120
24
60
x
12
5